Although the exercices were taken from manual for Bison 3.0.4, they were compiled and tested with version 3.0.2, when not with 2.4.1/MingW.

If noticing this version difference serves to any purpose, be it that the earlier version has a problem when using `%define api.value.type union` with `%defines` which results in a `YYSTYPE` definition in the header file containing duplicate members, while in the latter version should this problem have been fixed, or not. [It was, actually](http://savannah.gnu.org/forum/forum.php?forum_id=8188).

This anomaly has the obvious outcome of the C compiler rejecting the "malformed" union.

Within these practices the problem was gotten rid of by using, for the definition of the union, the `%union` declaration, which doesn't suffer this defect, with the appropriate changes in the rest of the code as it is changed the way to refer to semantic values (union members instead of C types).
